Signaling system



A. N. GOLDSMITH.

SIGNALING SYSTEM. APPLICATION lflLED MAY9, 1918.

1,404,756, Patented Jan. 31, 1922;

Inventor:

a flfr'ed n. Goldsmith,

w me UNITED STATES PATENT OFFICE.

ALFRED N. GOLDSMITH, or new YORK, N. Y., ASSIGNOR :ro GENERAL nnnc'rnrc. oomrnmr, A CORPORATION OF NEW YORK.

SIGNALING SYSTEM.

' Application filed May 9,

To all whom it may concern:

Be it known that I, ALFRED N. GOLDSMITH, a citizen of the United States, residing at New York, in the county of New York, State of New York, have invented certain new and useful Improvements in Signaling Systems, of which the following is a specification.

My present invention relates to signaling systems and more particularly to the controlling of the amplitude of the current supplied from a high frequency source to a radiating antenna system for the purpose of transmitting signals.

In case an oscillating loop circuit is supplied by a constant potential generator it is well known that a variation of the resistance of the loop will not appreciably change the current flowing therein if the reactanees composing the loop are large in comparison with the resistance. Hence, it is not practical to secure an effective control of the current in such a circuit merely by varying its resistance. The object of my invention is to provide an efiicient way of controlling the amplitude of the current in such a circuit in accordance with variations in the amplitude of a signaling current which will not be subject to this disadvantage which is inherent in the circuit.

In carrying out my invention I employ a variable resistance device in series with the circuit which feeds energy to the loop circuit. My invention may be utilized in a great variety of circuit organizations for transmitting various forms of signals and with different sources of radio frequency current. In case an electron discharge device of the pliotron type is employed for producing oscillations the loop circuit may be the output circuit of the pliotron. In this case I insert the variable resistance device in one of the leads which supply energy to the output circuit of the pliotron.

The novel features which I believe to be characteristic of my invention are pointed out with particularity in the appended claims. The "invention itself, however, both as to its organization and method of operation together with further objects and. advantages thereof will best be understood by reference to the following description taken in connection with the accompanying draw- Specifieation of Letters Patent. Patented J 31 1922 1918. Serial No. 233,661.

ing in which I have illustrated one way of carrying my invention into eifect.

I have indicated in the drawing a pliotron 1 comprising the usual filamentary cathode 2, anode 3 and grid 4 enclosed in an evacuated envelope. This pliotron is used for producin radio frequency oscillations. The anode an grid of the pliotron are connected to a loop circuit comprising an inductance 5 and a variable condenser 6 by means of which the circuit is tuned to the frequency of the oscillations which are to be produced. Energy for the operation of the oscillator is supplied by the direct current generator 7 which is connected to the cathode and anode, the cathode bein grounded at 8. Condenser 9 prevents the irect current component of the plate current from flowing through inductance 5. A choke coil 10 in series with the generator 7 prevents the radio frequency component of the plate current from flowing through the generator 7.

It will usually be desirable to apply to the grid a definite potential with respect to the cathode in order to adjust the normal current through the pliotron to a point on its operating characteristic which will be most favorable for its operation. This potential, which will usually be negative but which may be either positive or negative, may be obtalned from the battery 11, a radio frequency choke 'coil 12 being included in the circuit to prevent radio frequency currents from flowing through the battery 11. The condenser 13 will prevent the short circuiting of battery 11 through inductance 5.

The feed circuit for the resonant loop circuit 5, 6, is completed through a second pliotron 14, the anode 15 of which is connected to a point 17, in inductance 5 andthe cathode 16 of which is grounded at 18. If it is desired to modulate the radio frequency output of pliotron 1 to the antenna 19 1t is not possible to do so by varying the resistance of the oscillating circuit 5, 6, since with a constant potential supply the current through inductance 5 will remain substantially unchanged and hence the voltage mduced in antenna 19 will not vary. For example, I have found in one case that with no resistance in the oscillating circuit the current was 2.5 amperes while with a resistance of 18 ohms the current was only reduced to 2.1 amperes.

' voltage builds u This difliculty may be overcome, however, by varying the resistance of the feed circuit. In the arrangement shown this may conveniently be accomplished by varying the resistanceaof pliotron 14 by vary ing the potential of its grid 20 in accordance with the signals to be transmitted. In the case illustrated l have shown how the radio frequency current may be modulated in accordance with a telephone current from transmitter 21 which is applied to a grid circuit of pliotron 145 through a transformer 22. It will, or course, be understood that the system may equally well be employed for transmitting other forms of signals by merely impressing the desired form of signaling current on the grid circuit of pliotron 14, and that my invention is not limited to the use of the particular form of variable resistance shown. I

The operation of the circuit which I illustrated and described may be explained somewhat as follows:

When the circuit of generator 7 is closed direct current will start to flow through the pliotr'on 1- and at the same time a current impulse willcharge the condenser 9. This will cause a current impulse to flow through the upper halfof'coil- 5' and pliotron 14, producing momentary current in circuit 5, 6. As a result the pptential of the grid it will be changed and ischange in grid potential will vary the internal resistance of the pliotron. Assume, for example, that the resistance'1ncreases, that is the grid becomes more negative. The feeding current through the choke coil 10 tends to decrease, but the decrease is opposed by the counter electromot 'v'e force across coil 10 so that the direct current remains, the same, but a reactance across coil 10. This is added to the D potential of the generator 7, and,"therefore', in efiect the plate voltage oit'th'e pliotron' is increased. This increase In plate voltage causes a new rush ofcurrent througli'condenser 9 into coil 5 and pliotron -14:, and a correspondingly greater current in the circuit 5*, 6. This action will continue 'mitil the pliotr'on 1 has reached a substantially infinite resistance. The action then "decreases to' a low value,--when the grid 4 becomes strongly positive. In. this way oscillations will: be produced in the circuit 5, 6.

I- From another aspect the circuit 5, 6 may "be considered as a constant resistance sorelated to the variable resistance. of the plio tron 1 that it me variatiOnin the p iotron resistance. From periodically produce a this View the action may be considered as rollows':

- When the pliotron alternates in resistance .the' chokecoil 10 keeps the direct current trmfn the generator 7 substantially constant,

but the potential across the pliotronalternates. Hence in efi'ect the pliotron acts as having a terminal voltage which was constant over a considerable range of load.

What I claim as new and desire to secure by Letters Patent of the United States, is: 1. The combination in a signaling system of an electron discharge relay having an in candescent cathode, an anode and a grid enclosed inan evacuated envelope, a source of current and a high frequency choke coil connected between cathode and anode, a resonant loop circuit connected to the anode and grid of said relay in such a way that high frequency oscillations may be produced in said loop circuit, a second electron discharge e.

relay similar to the first having its also connected to an intermediate point in the inductance of said loop circuit and its cathode and capacity connected in parallel to the anode and grid of said relay, a circuit con nection between the cathode of sand relay and an intermediate point in the inductance.

of said loop circuit,. a' second electron dis charge relay similar to the first having its cathode and'anode' included'in, said circuit connection, and means for varying the p0 tential of the grid of said second relay in ac- -'cordance'with variations in a signaling. current.

3. The combination in a signaling-system of an electron discharge relay having in- 'candescent cathode, an anode, and a grid en closed in an evacuated envelope, a resonant 100p circuit connectedto the anode and grid,

of said relay in such a way that high frequency oscillations may be produced in said loop circuit, a circuit for feeding energy to said loop circuit connected to an intermediate point in the inductance of said loop circuit and including a source or direct-cure.

rent and a high frequency chokecoil, and means for varying the resistance of said feed circuit accordance with variations in a signaling current.

4. Thecombination in a al system of an electron discharge" relay having an incandes'cent cathode, an anode and a grid ere closed in an evacuated envelope, aresonant loop circuit connected to said relay in such a way that high frequency oscillations-may be produced therein, a circuit for feeding energy to said loop circuit connected to an intermediate point in the inductance of said loop circuit and including a source of direct current and a high frequency choke coil, and means for varying the resistance of said feed circuit in accordance with variations in a signaling current.

5. The combination in a signaling system of a resonant loop circuit, a circuit connected to an intermediate point in the inductance of said loop circuit and including a substan 10 tially constant potential source for feeding energy to said loop circuit to produce high frequency oscillations therein, a high frequency choke coil in said circuit connection, and means for varying the resistance of said feed circuit in accordance with variations in a signaling current.

In witness whereof, I have hereunto set my hand this 7th day of May, 1918.

ALFRED N. GOLDSMITH. 

